A1 Refereed original research article in a scientific journal
Optical spectroscopy of BL Lacertae objects - Broad lines, companion galaxies, and redshift lower limits
Authors: Sbarufatti B, Falomo R, Treves A, Kotilainen J
Publisher: EDP SCIENCES S A
Publication year: 2006
Journal name in source: ASTRONOMY & ASTROPHYSICS
Journal acronym: ASTRON ASTROPHYS
Volume: 457
Issue: 1
First page : 35
Last page: 43
Number of pages: 9
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361:20065455
Abstract
Results. For seven of these objects, nuclear emission lines and/or absorption lines from the host galaxy were detected. In all the four cases where absorption lines were revealed, the host galaxy has been resolved with HST or ground-based imaging. The broad H-alpha luminosities (or their upper limits) of the BL Lacs are similar to those of radio-loud quasars. For two BL Lacs, spectroscopy of close companions indicates that they are at the redshift of the BL Lacs, and therefore physically associated and probably interacting. Five BL Lacs have a featureless spectrum. In these cases, we apply a new technique to derive lower limits for their redshift, which are consistent with the lower limits deduced from imaging.
Results. For seven of these objects, nuclear emission lines and/or absorption lines from the host galaxy were detected. In all the four cases where absorption lines were revealed, the host galaxy has been resolved with HST or ground-based imaging. The broad H-alpha luminosities (or their upper limits) of the BL Lacs are similar to those of radio-loud quasars. For two BL Lacs, spectroscopy of close companions indicates that they are at the redshift of the BL Lacs, and therefore physically associated and probably interacting. Five BL Lacs have a featureless spectrum. In these cases, we apply a new technique to derive lower limits for their redshift, which are consistent with the lower limits deduced from imaging.
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